The present invention relates to a hypodermic syringe, and more particularly to a safety hypodermic syringe, which enables the needle assembly to be received inside the syringe barrel after the service of the syringe.
Regular safety hypodermic syringes are made for enabling the user (nurse or doctor) to pull the needle assembly backwards to the inside of the syringe barrel after injection, preventing possible contamination of bacteria or virus through the needle cannula. Taiwan Patent #356013 discloses a similar design of safety hypodermic syringe. However, this design of safety hypodermic syringe is still not satisfactory in function. When pushing the plunger into engagement with the needle assembly, a minor vibration occurs, causing the patient to feel uncomfortable.